An inverter circuit used to control a motor, etc. converts a commercial Alternating-Current (AC) voltage into a Direct-Current (DC) voltage by a diode bridge, smoothens pulsating waves remaining in the converted DC voltage by a smoothing condenser, and inputs the smoothened DC voltage to an inverter to convert the DC voltage into an AC voltage.
Typically, the DC voltage is smoothened until the amplitude of pulsating waves little remains in the DC voltage input to the inverter, in order to prevent pulsating waves remaining in an AC voltage that is applied to the motor, etc. from adversely influencing the control of the motor, etc. For this reason, a smoothing condenser having large capacitance and a large volume is used.
However, a switching control method of preventing pulsating waves remaining in a DC voltage from adversely influencing the control of a motor although the amplitude of the pulsating waves is great has been developed, and accordingly, the capacitance of the smoothing condenser does not need to be as large as it was. Accordingly, an electrolytic condenser having large capacitance and a large volume can be replaced by a ceramic condenser or a film condenser having small capacitance and a small volume.
Patent Document 1 discloses an inverter device including: a diode bridge to rectify an input three-phase AC voltage into a DC voltage; an inverter unit to convert the DC voltage converted by the diode bridge into an AC voltage, and to output the AC voltage; an LC filter including an inductor Ldc connected between an output terminal of the diode bridge and an input terminal of a converter, and a condenser Cdc connected between input terminals of the inverter unit; a voltage detector to detect a voltage applied at both terminals of the inductor Ldc; and a controller to control the inverter unit, wherein the controller controls the inverter unit based on the voltage applied at both terminals of the inductor Ldc, detected by the voltage detector, so that the transfer characteristics of the input/output voltage of the inverter unit become a first order lag system.
Patent Document 2 discloses a power conversion apparatus including: a rectifier circuit configured with a diode device, and configured to rectify an AC voltage of a commercial frequency and to output the AC voltage to DC buses; an inverter configured with a semiconductor switching device, and configured to convert a voltage of the DC buses into AC, and to supply the AC to a load; a voltage clamp circuit configured with a series body of a resistor and a switch connected between the DC buses; and a switch control circuit configured to close the switch that opens normally when the voltage between the DC bus reaches a predetermined overvoltage or when there is probability that the voltage reaches the predetermined overvoltage in order to prevent the occurrence of a voltage exceeding the predetermined overvoltage between the DC buses.
Patent Document 3 discloses a power conversion circuit, wherein a controller controls opening/closing of a switching relay and switching of switching devices Trp, Ttp, Trn, and Ttn installed in at least two-phase upper and lower arms of a converter circuit connected to a three-phase AC power source and a condenser, closes the switching relay until inrush current can be suppressed after current starts flowing to the converter circuit, and controls switching of the switching devices Trp, Trn, Ttp, and Ttn so that current flows to the one-phase upper and lower arms, and no current flows to the remaining upper and lower arms.